Fish Swimbladder Research Articles

Extraction Hydrolysates from Larimichthys Polyactis Swim Bladder Using Enzymatic Hydrolysis

As a kind of biopolymer, hydrolysates of fish swim bladder, safer than those of land mammals, are widely used in food, cosmetics as well as pharmaceutical and biomedical fields for their biocompatibility, biodegradability, and weak antigenicity. To enhance hydrolysate production, in this paper, the papain and alcalase hydrolysis processes of larimichthys polyactis swim bladder were optimized with orthogonal experiments. With 89.5% hydrolysate yield, the optimal processing conditions for alcalase were solid-liquid ratio of 1:30, enzyme concentration of 0.7%, and extraction time of 6 h. As for papain, under the optimal processing conditions: solid-liquid ratio of 1:20, enzyme concentration of 0.5%, and extraction time of 8 h, the hydrolysate yield was 65.1%. To obtain higher hydrolysate yields, the ultrasonic pretreatments were implemented before the optimal enzyme hydrolysis processes. With ultrasonic waves of 100 W for 50 min, the hydrolysate yields were increased 2.1% (alcalase) and 4.5% (papain), respectively. The Fourier Transform Infrared (FTIR) spectroscopic analysis revealed that the hydrolysates extracted by papain exist in triple-helical forms. The Ultra-Violet (UV) absorption spectra indicated that the aromatic amino acids in the hydrolysates had strong absorptions in the wavelength range of 240 nm–300 nm. The results of this research demonstrate that the alcalase hydrolysates have better solubility in water and the solution is more stable under ambient temperature. However, the hydrolysates extracted by papain have a gel property and are insoluble in weak acid at room temperature, which is more suitable for applications in feedstock of biomedical.

Effects of dietary proline on swim bladder collagen synthesis and its possible regulation by the TGF‐β/Smad pathway in spotted drum, Nibea diacanthus

Swim bladder is an ideal source of collagen production in fish for improved human health. Proline (Pro) is the main proteinogenic amino acid needed for collagen production. However, the effects of Pro supplementation on the swim bladder collagen synthesis have rarely been evaluated in fish. We determined the effects of dietary Pro supplementation on swim bladder collagen synthesis and its possible signalling pathway in spotted drum, Nibea diacanthus. A total of 450 N. diacanthus (100 ± 3.05 g) were randomly assigned into six treatments and fed with diets supplemented with different levels of Pro (0, 2.5, 5, 7.5, 10 and 12.5 g/kg of dry diet, hereafter P0, P1, P2, P3, P4 and P5, respectively) for 8 weeks. At the end, we evaluated collagen synthesis in swim bladder and the expression of genes related to TGF-β/Smad pathway in the fish. Dietary Pro levels increased significantly the contents of crude protein, total collagen (TC) and the levels of some amino acids in swim bladder than the control diet (p < .05). The optimum amount of dietary Pro inclusion in diets for swim bladder collagen synthesis in N. diacanthus was 7.6 and 7.5 g/kg based on crude protein and TC in swim bladder, respectively. Dietary Pro levels increased significantly the proline 4-hydroxylase (P4H) content in fish serum, swim bladder, muscle and liver tissues than control (p < .05). The relative expression of collagen type I alpha 1 (COL1A1), alpha 2 (COL1A2) and mothers against decapentaplegic homolog 2 (Smad2) genes in liver and swim bladder initially increased significantly as the concentration of Pro and later decreased (p < .05). Similarly, the relative expression of transforming growth factor beta (TGF-β), P4Ha2 and P4Ha3 genes in the swim bladder increased significantly as dietary Pro levels increased (p < .05). Using K-means clustering analysis, dietary proline partly promoted collagen accumulation in swim bladder through upregulation of Smad2 and TGF-βRT genes. Taken together, Pro affected the collagen metabolism in swim bladder, probably by regulating the TGF-β/Smad pathway, most likely via transient overexpression of Smad2 gene.

Development and evaluation of a novel beneficent antimicrobial bioscaffold based on animal waste-fish swim bladder (FSB) doped with silver nanoparticles

Treated fish wastes have found many applications in industry and medicine. Besides, nowadays low-cost scaffold with antimicrobial activity which can accelerates the process of wound healing is very demanding. In this study fish swim bladder (FSB), taken from Rutilus frisii, which is a disposable waste was doped with silver nanoparticles (AgNPs) and evaluated as antimicrobial wound dressing. The scanning electron microscopy (SEM) micrographs showed the presence of AgNPs on the scaffold. Histological observation confirmed cells and muscle removal from FSB and collagen preservation. There was significant antibacterial activity even in 50 ppm AgNPs concentration against pathogenic bacteria, swelling ratio was rather low, and cytotoxic assay revealed that the AgNPs-FSB scaffold had no toxic effect on human foreskin fibroblast (HFF) cells. Interestingly, despite the porous structure, the AgNPs-FSB scaffold was found to be a suitable barrier to microbial penetration even after 72 h. Further study showed the gradual release of AgNPs during 24 h. In conclusion, biofabricated FSB prepared in this study have appropriate characteristics notably encompassing a high quantity of collagen and broad-spectrum antimicrobial activity. Also, its porous structure made it suitable as a 3-D structure for the growth of cells and adding other antimicrobial nano-sized materials.

Remote sizing of fish-like targets using broadband acoustics

Broadband echosounder systems provide very high range resolution that could resolve different parts of fish and hence provide estimates of fish size. The potential for, and accuracy of, direct acoustic sizing of fish was tested on fish-like targets of known dimensions and orientations. Prolate spheroids, 91–477 mm long, with and without an air-filled inclusion (simulating a fish swim-bladder), made from polyvinyl-alcohol-cryogel, were suspended in an acoustic beam and rotated while the backscattered signal was recorded. The echoes from linear frequency modulated pulses of 45−90 and 160−260 kHz with a fast and a slow amplitude modulation were pulse-compressed to provide data with a range resolution of 6.6 mm at its highest. Echoes from the target boundaries were manually identified, tracked and used to directly estimate the thickness and length of the targets. An accuracy of ±11−17 mm was achieved for targets longer than about 200 mm and thicker than about 20 mm when using the 160−260 kHz pulse. The length of the air-filled inclusion could also be estimated for the larger targets. Echoes from the slow amplitude modulation were easier to interpret than the fast amplitude modulation despite the lower range resolution, due to the lower pulse compression temporal sidelobes. The results show that remote acoustic sizing of fish is feasible and of sufficient accuracy for practical use.

Enhancement of collagen deposition in swim bladder of Chu's croaker (Nibea coibor) by proline: View from in-vitro and in-vivo study

The market demand of collagen has been increasing over years as its wide application in food, comestic and biomedicine industries. Swim bladder is an ideal optional source for collagen production and has long been considered as a traditional tonic in China. Therefore, strategies to improve collagen content in the swim bladder would confer to producing products with high nutrition and economic value. However, little was known in the regulatory mechanism on collagen deposition in fish, especially in the swim bladder. Here, we reported an in-vivo and in-vitro study of proline's effects on collagen deposition in a famous economic marine fish, Chu's croaker (Nibea coibor) for the first time. It was demonstrated that proline significantly improved collagen content in the swim bladder of N. coibor, although no obvious enhancement in growth performance was observed. By RNA-sequencing and qRT-PCR, several genes involved in collagen biosynthesis (Col1a1, Col1a2 and CTGF) and degradation (TIMP2) were identified and validated to be up-regulated in the swim bladder of fish fed with proline supplementation. Furthermore, the effects of proline on collagen deposition and related gene expression were confirmed in swim bladder cell of N. coibor. These results suggested that proline promoted collagen deposition in swim bladder mainly through enhancing collagen biosynthesis and inhibiting collagen degradation. Our data would help to understand the molecular mechanism of collagen deposition in the species and develop new strategies of producing fish products with higher quality.

Bio-Inspired Soft Swim Bladders of Large Volume Change Using Dual Dielectric Elastomer Membranes

AbstractThe buoyancy control mechanism is critical for undersea robots to achieve effective vertical motion. However, current buoyancy control mechanisms are associated with problems such as complex design, bulky structure, noisy operation, and slow response. Inspired by the swim bladder of natural fish, we develop an artificial swim bladder, using dual membranes of the dielectric elastomer, which exhibit interesting attributes, including fast response, light weight, silent operation, especially large volume change. Both the experiments and theoretical simulations are conducted to analyze the performance of this artificial swim bladder, and they quantitatively agree with each other. This artificial swim bladder of dual membranes is capable of large voltage-induced volume change, 112% larger than the conventional single-membrane design. Consequently, this soft actuator can generate a buoyancy force of 0.49 N. This artificial swim bladder demonstrates effective up-and-down motion in water, due to its large reversible volume change. Future work includes adding horizontal-motion and turning capabilities to the existing robotic structure, so that the soft robotic fish can achieve successful navigation in undersea environments.

Ecological Poetics; or, Wallace Stevens’s Birds by Cary Wolfe

Reviewed by: Ecological Poetics; or, Wallace Stevens’s Birds by Cary Wolfe Joshua Corey Ecological Poetics; or, Wallace Stevens’s Birds. By Cary Wolfe. Chicago: The University of Chicago Press, 2020. In his new book, Cary Wolfe, a scholar of poetics in the American grain turned bioethicist and thought leader in the new field of posthumanism, cogently and often brilliantly rereads Wallace Stevens as a practitioner of what we might call second-order ecopoetics—a poetry that is less interested in describing the natural world than it is in demonstrating and enacting on a stylistic level what Timothy Morton has called “ecological thought.” For Wolfe, the otherness of “nature” in Stevens’s late work, as in Emerson’s, is a phantom, a reified and ideological image that conceals the environmental thinking of a poetics constantly returning to an insight disclosed by systems theory: “what look like opposites on the surface of things—subject vs. object, let’s say, or mind vs. nature—turn out, upon closer inspection, to share a deeper, paradoxical unity. They are two sides of a distinction that gives form to the world, but here ‘form’ is indissociable from function, enaction, and performativity” (ix; italics in original). As Stevens said in a quotation to which Wolfe often returns, “it is not [the poet’s role] to lead people out of the confusion in which they find themselves. . . . His role . . . is to help people to live their lives” (CPP 660–61). Living poetically, for Wolfe’s Stevens, takes place in and through the confusion or fusion of imagination and reality, the observer and the observed, the human and the inhuman. This comparatively short book is dense with divergent discourses masterfully handled by Wolfe, who proves himself as familiar with canonical Stevens criticism (by Helen Vendler, Harold Bloom, J. Hillis Miller, and others) as he is agile with the terminology of theoretical biology, Derridean deconstruction, Niklas Luhmann’s systems theory, and Peter Sloterdijk’s wildly ambitious philosophical trilogy Spheres. At the center of Wolfe’s argument is “a nonrepresentationalist understanding of poiesis: whether we are talking about the poiesis of ‘life’ and the evolution of the biosphere in theoretical biology, or the poiesis of worlding and world-making in deconstruction, or the poiesis of Stevens’s poetic practice” (61; italics in original). Wolfe’s third chapter demonstrates morphological similarities between Derridean deconstruction and theoretical biology, both of which critique models of representational truth and propose instead, in the words of sociologist Vicki Kirby, that “the one who knows, the measuring apparatus and the object to be interpreted are strangely involved” (qtd. on 62). Building upon the work of Christopher Johnson, whose System and Writing in the Philosophy of Jacques Derrida outlines some of the “crosstalk between deconstruction and the life sciences” (69), Wolfe argues that the object of knowledge in deconstruction behaves like a living organism that derives its activity from the interchange with its environment, its meaning irreducible to and unexhausted by our understanding of that environment; he writes that [End Page 289] “Derrida gives us a theory of something like the relationship of the genetic (or systemic, formally code-bound) and the epigenetic factors (the environmental or contextual setting in which the code is deployed)” (72). Deconstruction, in other words, is an evolutionary discourse. Wolfe cites Matthias Fritsch’s summary of Derrida’s key neologism, différance: “The term is to encompass difference and deferral—that is, situation in context but without final determinability, anticipation of future environments (for not anything goes), but also exposure to the open-ended future the elements in an ongoing system cannot know” (qtd. on 71). From here it is but a short step to the key Darwinian concept of exaptation, by which a trait developed by a species in response to environmental conditions shifts its function, as in the example Wolfe adapts from Stuart Kauffman of the swim bladder in fish: “The Darwinian exaptation whereby some early versions of fish had lungs, enabling them to bounce from puddle to puddle, led in time to the biological function of a ratio of air and water in fish that now live wholly in water that allows neutral buoyancy in the water column” (79...

Marketing of Dried Swim Bladder of Fishes (Vesica Natatorium) in or on Local Government Area, Akwa Ibom State, Nigeria

In the last two decades, there has been a land slide movement towards markets liberalization in the world. Although the pace and depth of liberalization have varied both in international and domestic markets, but no continent remains untouched [1].

Fisheries in Merauke: linking fishermen to markets

The Indonesian Minister of Marine and Fisheries Regulations has given a prospect for domestic fishing vessels and Merauke as the stay over fishing port. This study found that in Merauke the capacity of cold storage was only 2,250 tons; the shortage of ice supply for fishing remains occurred; most of the fishing fleets were not equipped with freezer and; the fish-processing unit did not exist. As a consequence, 13.42% - 51.5% of fishes were thrown away to the sea after taking the swim bladder of fish (fish maw). Data and information on fisheries were collected from 23 April 2019 to 3 May 2019 in Merauke. The supply chain approach was used for policy intervention to improve the fishing business. The objective of this study was to analyze the phenomenon of fishery business in Merauke. The main conclusion of the analysis show, Merauke become a landing place for fish maw’s fishing fleets from the Arafura Sea. This study recommended that there must be an investor to organize a 100 tons ice factory as a supplier for fishing vessels. Merauke might be promoted as the center for pet food industries by using discarded fish to fill domestic market demand. Promote local traders to follow domestic and international fish trade exhibition to prepare Merauke as the business center of fish maw.

A Bio-Hygromorph Fabricated with Fish Swim Bladder Hydrogel and Wood Flour-Filled Polylactic Acid Scaffold by 3D Printing.

Non-powered adaptive systems are attractive in the construction of environment actuators, meteorosensitive architectures, biomedical devices, and soft robotics. Combining hydrophilic materials and anisotropic structures to mimic self-morphing plant structures has been demonstrated as an effective approach to creating artificial hygromorphs. The convenience of 3D printing technologies in shaping programmable complex structures facilitates the imitation of complex anisotropic plant structures. In this research, we constructed a bio-hygromorph using fish swim bladder hydrogel as the hydrophilic material and wood flour-filled polylactic acid (WPLA) scaffold, which was printed with fused deposition modeling (FDM) 3D printing technology (3DP). The environmental benign bio-hygromorph displayed morphing abilities triggered by moisture content changes, as the fish swim bladder hydrogel swelled and shrunk during absorption and desorption cycles. The strain disproportion of the two-layered composite structure in the bio-hygromorph drove the bending deformation. Stress analyses performed with finite element analysis (FEA) also revealed the mechanism behind the moisture content driven morphing of the bio-hygromorph. Notably, the bio-hygromorph exhibited faster response times to moisture absorption than desorption, which may donate actuators’ different attributes in distinct moisture conditions.

Study on the preparation and physicochemical properties of fish swim bladder membrane

To manufacture fish swim bladder membrane material by crosslinking techniques, and to explore its physical and chemical properties and cytotoxicity. After decellularization, the swim bladders were randomly divided into two groups. The swim bladders were treated with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS) crosslinking method, surface hole making, and freeze-drying in crosslinking group, and only surface hole making and freeze-drying in non-crosslinking group. The physical and chemical properties of the materials were observed, including microstructure by scanning electron microscopy (SEM), mechanical properties (tensile strength and breaking elongation) by universal tensile machine, hydrophilicity by contact angle measuring instrument, porosity by ethanol infiltration method, degradation performance in vitro and thermal stability test, and the components of materials by infrared spectrum analysis. Mouse fibroblasts (L929) were cultured with the extracts of two groups of materials in order to determine the cytotoxicity of materials by using cell counting kit 8 (CCK-8) method. The porous structure and rough surface of materials were observed by SEM. Compared with the non-crosslinking group, the tensile stress of the crosslinking group was higher, the breaking elongation was lower, and the porosity increased, showing significant differences ( P<0.05). There was no significant difference in contact angle between the two groups ( P>0.05). The degradation was faster within the first 7 days and then tended to be smooth in the two groups. But the degradation rates of crosslinking group were significantly lower than those of non-crosslinking group ( P<0.05). Differential scanning calorimeter showed that the denaturation temperature of the crosslinking group was (75.2±1.3)℃, which was significantly higher than that of the non-crosslinking group [(68.5±0.4)℃] ( t=4.586, P=0.002). Compared with the non-crosslinking group, the crosslinking group produced new C=O bond and N-H bond, and no other new groups were introduced into the cross-linking group. CCK-8 method showed that the absorbance values of the crosslinking group and the non-crosslinking group were not significant when compared with the positive control group ( P>0.05). The fish swim bladder membrane obtained by crosslinking treatment with EDC/NHS method has good physical and chemical properties, no cytotoxicity, and is expected to be used as a dura mater repair material.

Effect of swim bladder matrix treated with hyaluronic acid on wound healing: an animal model evaluation.

To investigate the potential restorative effects of the white fish (Rutilus frisii kutum) swim bladder matrix (FSBM) treated with hyaluronic acid (HA) in the repair of skin wounds in an animal model. Wistar rats were used to investigate the repair function of FSBM as a biological scaffold. Rats were given four round wounds on their back. Wounds were divided into four groups: control, acellular fish swim bladder matrix (AFSBM), HA and AFSBM impregnated with HA (AFSBM-HA). Macroscopic and histological studies in wound healing were investigated on days three, five and seven after injury. The AFSBM-HA group showed a rapid reduction in wound area compared with the other groups, indicating faster wound healing (p<0.001). At day seven after injury, the AFSBM group showed a faster process in epidermal layer formation and angiogenesis compared with the control group (p<0.001). In the AFSBM-HA group, in addition to the reduction of inflammatory cells density, a significant increase in the number of fibroblast cells and collagen synthesis was observed. An elevation in collagen synthesis and angiogenesis was also observed in the HA group compared with the control group. The findings of this study indicate that AFSBM-HA can potentially be used as a biological dressing in wound healing.

Гидролизаты коллагена, полученные из плавательного пузыря северных рыб, как модификаторы морозостойких резин уплотнительного назна-чения

Гидролизаты коллагена, полученные из плавательного пузыря северных рыб, как модификаторы морозостойких резин уплотнительного назна-чения

Metaplasia in swim bladder epithelium of the endangered annual fish Austrolebias nigrofasciatus (Cyprinodontiformes: Rivulidae) results in inadequate swimming and delayed growth

ABSTRACT Laboratory breeding of annual fish is often impaired when fish fail to inflate the swim bladder after hatching. These fish, which are known as belly-sliders, cannot swim in the water column, moving mainly on the bottom of water. Therefore, we wanted to understand the factors underlying failed inflation of swim bladder in the annual fish Austrolebias nigrofasciatus and determine the implications of this condition on the growth of juveniles. To identify how the initial filling of the gaseous vesicle is compromised, and to determine the implications of this condition on juvenile growth, we analysed the histology of the swim bladder of both normal swimming fish and belly-sliders during their initial growth phase (first month of life). In addition to slower growth rate compared with fish swimming normally, we found that belly-sliders have metaplasia characterized by epithelium peeling of the swim bladder and the presence of haemorrhage. Based on our findings, it can be concluded that metaplasia of the swim bladder is recurrent in annual fish bred in the laboratory, which explains the large number of unviable larvae. However, its causes remain unknown.

Assessment of injury and mortality from rapid decompression on crucian carps

Knowledge of barotrauma injury mechanisms is required in the fish-friendly turbine design. Rapid decreases in pressure is one of the main reasons that cause injury and mortality to fish that pass through hydropower machines. A steel tank and related pressure regulation components were designed to study the barotrauma injury thresholds of crucian carps. Decompression from 700 kPa to 6 kPa in 0.3 s was implemented in this system with dozens of yearling and subyearling crucian carps. The fish swim bladder and other organs were observed to find the main reason for injury after the rapid decompression. The tested fish were kept for at least 48 hours to study the physiological status in different observation periods. The direct and indirect decompression induced mortality after the test was observed and analyzed.

From siphonophores to deep scattering layers: uncertainty ranges for the estimation of global mesopelagic fish biomass

AbstractThe mesopelagic community is important for downward oceanic carbon transportation and is a potential food source for humans. Estimates of global mesopelagic fish biomass vary substantially (between 1 and 20 Gt). Here, we develop a global mesopelagic fish biomass model using daytime 38 kHz acoustic backscatter from deep scattering layers. Model backscatter arises predominantly from fish and siphonophores but the relative proportions of siphonophores and fish, and several of the parameters in the model, are uncertain. We use simulations to estimate biomass and the variance of biomass determined across three different scenarios; S1, where all fish have gas-filled swimbladders, and S2 and S3, where a proportion of fish do not. Our estimates of biomass ranged from 1.8 to 16 Gt (25–75% quartile ranges), and median values of S1 to S3 were 3.8, 4.6, and 8.3 Gt, respectively. A sensitivity analysis shows that for any given quantity of fish backscatter, the fish swimbladder volume, its size distribution and its aspect ratio are the parameters that cause most variation (i.e. lead to greatest uncertainty) in the biomass estimate. Determination of these parameters should be prioritized in future studies, as should determining the proportion of backscatter due to siphonophores.

Helminths of European smelt Osmerus eperlanus (Linnaeus, 1758) in Lake Hańcza and the Vistula Lagoon, with special regard to their zoonotic threats

Reports published in recent years on the increased risk in the Baltic Sea of fish infection with larvae of nematodes potentially pathogenic to humans have prompted a study of European smelt Osmerus eperlanus with respect to the presence of these parasites in the Vistula Lagoon. Additionally, samples of this fish from Lake Hańcza were comparatively considered. The body cavity, the surface of internal organs, the alimentary tract and the swimbladder of fish from two environmentally different water bodies were taken into account in the analysis. Only the tapeworm Proteocephalus longicollis was found in the alimentary tract of the fish from Lake Hańcza. Depending on the period of study, the prevalence ranged from 60% to 100%, and the mean intensity from 11.5 to 42.0. The helminth fauna of smelt from the Vistula Lagoon was more diverse: Cystidicola farionis occurred with a prevalence from 25.9 to 75.0% and a mean intensity of infection from 2.7 to 66.0%, Proteocephalus longicollis and cystacanths of Corynosoma with a prevalence ranging in different years from 12.0 to 44.0% and from 14.8 to 50.0%, respectively. Zoonotic parasites, such as nematode larvae of the Anisakidae family (Contracaecum sp., Anisakis simplex), occurred in the intestine with a prevalence of 31%, 72% and 22% in consecutive years of the study.

Divided swim bladder maintains brooding cichlid mum's balance

When Astatotilapia burtoni females lay eggs, they don't simply turn their backs and make a quick exit. The soon-to-be mothers vacuum the eggs up into their mouths, where the youngsters develop and grow before they are ready to depart 14 days later. But the sudden weight shift, amounting to as much as 30% of the female's weight, could seriously destabilise brooding mums and the situation could become even more perilous as the larvae and fry become heavier and more negatively buoyant during development. Yet, the mothers seem to take the inconvenience in their stride and never topple forward. Knowing that the fish's swim bladder is divided into two compartments, Julie Butler, Prosanta Chakrabarty and Karen Maruska from Louisiana State University, USA, wondered whether the fish may adjust the distribution of gas between the two parts of the swim bladder to compensate when they become front heavy.Butler, Sarah Whitlow and Polly Gwan collected female A. burtoni that were ready to spawn large eggs, at various stages over the 14 day brooding period, and 1 and 3 weeks after the fry sallied forth, and then X-rayed the fish. Comparing the X-ray images, the team could see that the overall area of the swim bladder did not alter during the development of the offspring; however, the distribution of gas between the two compartments did shift. The front section expanded while the rear section deflated when the females slurped up their eggs and remained so until the youngsters left their mother's mouths 2 weeks later. Then, the front section of the swim bladder deflated and the rear section reinflated. The team also monitored the fish's swimming posture when the fry were liberated, and found that the unencumbered females’ heads bob upwards, so that the fish swam at an angle of 7 deg for 5 min until they resumed their pre-release almost-horizontal posture. And when the team attached a small bead weighing roughly the same as a mouthful of 7-day-old fry to the underside of the jaws of females that were not brooding, they saw the same shift in the swim bladder shape 4 h later.Considering the cichlid's rapid reaction to their sudden weight redistribution, the team suspects that the fish redistribute gas between the two parts of the swim bladder by opening and closing a ring of muscle in the diaphragm that separates the two. As tissue in the front section of the swim bladder produces gas, while tissue in the rear section removes gas from the swim bladder, the team suggests that the sphincter in the diaphragm closes when the fish suck the eggs into their mouths, allowing gas to inflate the front section to counteract the weight of the eggs. When the mothers release the fry, they can then restabilise their posture by rapidly opening the sphincter to drain gas into the rear compartment of the swim bladder. And the team suggests that a compartmentalised swim bladder could be an essential adaptation for fish that prefer to give their young a head start in their mouths.

Comparative transcriptome analysis reveals conserved branching morphogenesis related genes involved in chamber formation of catfish swimbladder.

The swimbladder is an internal gas-filled organ in teleosts. Its major function is to regulate buoyancy. The swimbladder exhibits great variation in size, shape, and number of compartments or chambers among teleosts. However, genomic control of swimbladder variation is unknown. Channel catfish ( Ictalurus punctatus), blue catfish ( Ictalurus furcatus), and their F1 hybrids of female channel catfish × male blue catfish (C × B hybrid catfish) provide a good model in which to investigate the swimbladder morphology, because channel catfish possess a single-chambered swimbladder, whereas blue catfish possess a bichambered swimbladder; C × B hybrid catfish possess a bichambered swimbladder but with a significantly reduced posterior chamber. Here we determined the transcriptional profiles of swimbladder from channel catfish, blue catfish, and C × B hybrid catfish. We examined their transcriptomes at both the fingerling and adult stages. Through comparative transcriptome analysis, ~4,000 differentially expressed genes (DEGs) were identified. Among these DEGs, members of the Wnt signaling pathway ( wnt1, wnt2, nfatc1, rac2), Hedgehog signaling pathway ( shh), and growth factors ( fgf10, igf-1) were identified. As these genes were known to be important for branching morphogenesis of mammalian lung and of mammary glands, their association with budding of the posterior chamber primordium and progressive development of bichambered swimbladder in fish suggest that these branching morphogenesis-related genes and their functions in branching are evolutionarily conserved across a broad spectrum of species.

Glycosaminoglycans from fish swim bladder: isolation, structural characterization and bioactive potential.

The swim bladder of fish is an internal gas-filled organ that allows fish to control their buoyancy and swimming depth. Fish maws (the dried swim bladders of fish) have been used over many centuries as traditional medicines, tonics and a luxurious gourmet food in China and Southeast Asia. Little is known about the structural information of polysaccharides comprising this important functional material of fish tissue. In the present study, the total glycosaminoglycan (GAG) from fish maw was characterized. Two GAGs were identified, chondroitin sulfate (CS, having a molecular weight of 18-40kDa) and heparan sulfate (HS), corresponding to 95% and 5% of the total GAG, respectively. Chondroitinase digestion showed that the major CS GAG was composed of ΔUA-1→3-GalNAc4S (59.7%), ΔUA-1→3-GalNAc4,6S (36.5%), ΔUA-1→3-GalNAc6S (2.2%) and ΔUA-1→3-GalNAc (1.6%) disaccharide units. 1H-NMR analysis and degradation with specific chondroitinases, both CS-type A/C and CS-type B were present in a ratio of 1.4:1. Analysis using surface plasmon resonance showed that fibroblast growth factor (FGF)-2 bound to the CS fraction (KD=136nM). These results suggest that this CS may be involved in FGF-signal pathway, mediating tissue repair, regeneration and wound healing. The CS, as the major GAG in fish maw, may have potential pharmacological activity in accelerating wound healing.